Lower air dam



FIG. 1 is a front perspective view of a lower air dam showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a top view thereof.

The broken lines shown in the drawings illustrate portions of the lower air dam that form no part of the claimed design. 

CLAIM The ornamental design for a lower air dam, as shown and described. 